1. Field of Invention
This invention relates to novel dentures and to a method for preparing the same. It is particularly directed to novel dentures in which the teeth are formed of hard polyurethane elastomer and the gums of soft polyurethane elastomer.
2. Prior Art
It has been proposed to provide dentures with a soft layer in contact with the gums and other mouth parts to provide tissue relief. Such soft layers have been composed of acrylics, silicones, and like rubber-like materials. But on aging, such soft layers tend to harden and give off undesirable odors. In addition, some decomposition of the polymer may also occur presumably due to an oxidation process as well as to pH fluctuations within the mouth.
Also, in order to provide a unitary structure in which the teeth are firmly imbedded in the gum portion of the dentures, various types of holding means such as pins, rods, diotorics, that is, undercut channels or holes, are provided so that the teeth become firmly imbedded in the denture material.